The present invention relates to a rotary vane pump assembly of the type adapted to provide a partial vacuum for operation various automobile accessories. A pump of this general type is disclosed in U.S. Pat. No. 4,451,215 and published UK Patent Application GB No. 2,074,247.
German patents OS Nos. 30 14 519 and 30 14 520 disclose rotary vane vacuum pumps, wherein a freely rotatable sleeve is disposed on the inner periphery of the outer housing. The use of such a sleeve permits the sliding speed of the ends of the vanes to be substantially reduced, and the reduced sliding speed permits the usual oil lubrication to be omitted, and as a result, the exhaust air is substantially free of oil. This design however cannot be used for the so-called external rotor type pumps, wherein the housing forms both the vane carrier and the rotor, and eccentrically encloses the stator, because in this instance the supply and/or discharge lines normally would be located in the stator and terminate on its circumferential surface, and the presence of a rotatable sleeve on the stator would block the openings of the supply and discharge lines.
Vacuum pumps are often employed to assist the braking power and to operate other accessories in motor vehicles having Diesel engines or Otto injection engines, and these vacuum pumps are commonly of the rotary vane type. It is also recognized that other components of the automobile, such as lubricating oil pumps, hydraulic pumps, or electric generators are needed for the operation of the vehicle. All of these accessories are driven by the engine of the motor vehicle, and it is difficult to accommodate all of these accessories in the engine compartment by reason of limited space, and in addition, the drives are ditticult to connect to the engine because of space limitations. Problems also arise with respect to the supply of lubricating oil to these accessories, since lubricating oil must be both supplied and discharged. Further, the operation of a rotary vane vacuum pump having an internal oil lubrication system can present problems, since the lubricating oil must be prevented from exiting with the exhaust air into the atmosphere where it may contact adjacent accessories. In particular, in the case of an electric generator, it is absolutely necessary to avoid any contact with such lubricating oil.
It is accordingly an object of the present invention to provide a rotary vane pump of the external rotor type, which does not require an internal oil lubrication system, and so that the air output is substantially oil free.
It is also an object of the present invention to provide a rotary vane pump assembly which comprises a unitary structure composed of a rotary vane vacuum pump and another machine, such as an automobile accessory, and wherein the structural assembly is compact and requires only one common drive connection from the engine.